Motor vehicles, such as, for example, hybrid vehicles use multiple propulsion systems to provide motive power. This most commonly refers to gasoline-electric hybrid vehicles, which use gasoline (petrol) to power internal-combustion engines (ICEs), and electric batteries to power electric motors. These hybrid vehicles recharge their batteries by capturing kinetic energy via regenerative braking. When cruising or idling, some of the output of the combustion engine is fed to a generator (merely the electric motor(s) running in generator mode), which produces electricity to charge the batteries. This contrasts with all-electric cars which use batteries charged by an external source such as the grid, or a range extending trailer. Nearly all hybrid vehicles still require gasoline as their sole fuel source though diesel and other fuels such as ethanol or plant based oils have also seen occasional use.
Batteries and cells are important energy storage devices well known in the art. The batteries and cells are typically comprised of electrodes and an ion conducting electrolyte positioned therebetween. For example, the rechargeable lithium ion cell, typically comprises essentially two electrodes, an anode and a cathode, and a non-aqueous lithium ion conducting electrolyte therebetween. The anode (negative electrode) can be a carbonaceous, or metallic, or metal alloy electrode that is capable of intercalating lithium ions. The cathode (positive electrode), a lithium retentive electrode, is also capable of intercalating lithium ions. The anode comprises any of the various materials such as carbon (e.g., graphite, coke, carbon fiber, etc.), mixed metal oxides (such as Li4Ti5O12 or silicon oxide), metals (such as Si or Sn), metal alloy (such as Si/Sn alloys) which are capable of reversibly storing lithium species, and which are bonded to an electrically conductive current collector (e.g., copper foil) by means of a suitable organic binder (e.g., polyvinylidine fluoride, PVdF). The cathode comprises such materials as transition metal oxides or chalcogenides that are bonded to an electrically conducted current collector (e.g., aluminum foil) by a suitable organic binder. Oxide of chalcogenide compounds include oxides, sulfides, selenides, and tellurides of such metals as vanadium, titanium, chromium, copper, molybdenum, niobium, iron, nickel, cobalt, and manganese. Lithiated transition metal oxides are, at present, the preferred positive electrode intercalation compounds.
Examples of suitable cathode materials include LiMnO2, LiCoO2, LiNiO2, and LiFePO4, their solid solutions and/or their combination with other metal oxides and dopant elements, e.g., titanium, magnesium, aluminum, boron, etc. The electrolyte in such lithium ion cells comprises a lithium salt dissolved in a non-aqueous solvent which may be (1) completely liquid, (2) an immobilized liquid (e.g., gelled or entrapped in a polymer matrix), or (3) a pure polymer. Known polymer matrices for entrapping the electrolyte include polyacrylates, polyurethanes, polydialkylsiloxanes, polymethacrylates, polyphosphazenes, polyethers, polyvinylidine fluorides, polyolefins such as polypropylene and polyethylene, and polycarbonates, and may be polymerized in situ in the presence of the electrolyte to trap the electrolyte therein as the polymerization occurs.
Known polymers for pure polymer electrolyte systems include polyethylene oxide (PEO), polymethylene-polyethylene oxide (MPEO), or polyphosphazenes (PPE). Known lithium salts for this purpose include, for example, LiPF6, LiClO4, LiSCN, LiAlCl4, LiBF4, LiN(CF3SO2)2, LiCF3SO3, LiC(SO2CF3)3, LiO3SCF2CF3, LiC6F5SO3, LiCF3CO2, LiBOB, LiAsF6, and LiSbF6. Known organic solvents for the lithium salts include, for example, both cyclic and linear carbonate esters (such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate), cyclic ethers, cyclic esters, glymes, cyclic esters, formates, esters, sulfones, nitrates, and oxazoladinones. The electrolyte is incorporated into pores in a separator layer between the anode and the cathode. The separator layer may be either a microporous polyolefin membrane or a polymeric material containing a suitable ceramic or ceramic/polymer material.
The art is replete with various designs of conventional lithium batteries, which present a polymer soft pack batteries that uses prismatic or cylindrical cans or rectangular boxes as a package for the battery cells as seen by reference to the U.S. Pat. No. 5,639,571 to Waters, et al.; U.S. Pat. No. 6,120,935 to Van Lerberghe; U.S. Pat. No. 6,368,743 to Guerin et al. and the United States Patent Publication Nos. 2002/0045096 to Sandberg et al.; 20050123828 to Oogami et al.; 20050271934 to Kiger et al.; and 20040115519 to Lee et al. disclose other designs of battery packs.
The United States Patent Publication No. 20050271934 to Kiger et al. teaches a low-profile battery pack having an electrolyte barrier. The pack includes a plurality of rechargeable cylindrical cells, being arranged in end to end pairs of two cells. A cleavage void formed by the convex geometry of the cells accommodates at least one insulator and a first circuit board. Tabs couple the cells to the first circuit board. A flexible substrate couples the first circuit board to a second circuit board. The assembly is then placed in a housing having a first compartment and a second compartment, such that the cells are placed in the first compartment and the second circuit board is placed in the second compartment. Between the first and second compartments exists an electrolyte barrier.
Due to this adjacent arrangement, the aforementioned cleavage void is formed between the intersection line and a plane running across the top of each cell so as to be tangent to the convex curvature of each cell. The cleavage void is essentially a triangular shaped space, where the triangle has two concave sides. Alluding to the above, the insulator taught by the United States Patent Publication No. 20050271934 to Kiger et al. is a plastic member that has a geometric cross-section that fits within the cleavage space. The cross sectional shape is generally triangular, with two of the sides having concave curvatures to mate between a pair of cylindrical cells. The insulator is a separate element and is not an integral part of the cells. The insulator taught by the United States Patent Publication No. 20050271934 to Kiger et al. is specific to the cells having circular configuration.
The United States Patent Publication No. 20050123828 to Oogami et al. teaches a unit cell, formed in a flat shape in the presently filed embodiment, internally includes an electric power generating element comprised of a positive electrode plate, a negative electrode plate and a separator, all of which are stacked in such order. The unit cell forms a secondary battery, such as a lithium ion secondary battery, employing a gel polymer electrolyte. With the unit cell, a laminate film with a three-layer structure is used as an outer sheath and formed in three layers that include an aluminum foil interposed between resin films each made of polyamide resin.
Alluding to the above, the unit cell has the positive electrode tab and the negative electrode tab as tabs forming output terminals extending in a direction perpendicular to the stack direction. The positive electrode tab and the negative electrode tab are extracted outside an outer sheath. Formed in the positive electrode tab and the negative electrode tab, respectively, are holes, to which insulator pins, each having a surface subjected to insulation treatment, are inserted. The unit cells are alternately stacked such that the electrode tabs have positive and negative polarities alternately arranged in the stack direction, i.e., the positive electrode tab and the negative electrode tab are alternately stacked. The electrically conductive washers and the insulation washes are alternately set through the insulator pins such that the positive electrode tabs and the negative electrode tabs are sandwiched. In particular, the insulation washer is interposed between the positive electrode tab and the negative electrode tab layered thereon, and the electrically conductive washer is interposed between the negative electrode tab and the positive electrode tab layered thereon.
The insulation washer is placed on the positive electrode tab and the electrically conductive washer is placed on the negative electrode tab. Incidentally, although the electrically conductive washer and the insulation washer are located on the positive electrode tab and the negative electrode tab of the unit cell remaining in the uppermost layer, respectively, in dependence on a sequence in which the electrode tabs are arranged, it doesn't matter if these component parts are dispensed with depending on circumstances. Similar to the unsulator taught by the United States Patent Publication No. 20050271934 to Kiger et al., the insulator of the United States Patent Publication Nos. 20050123828 to Oogami et al. present a separate element, which is not an integral part of the cells.
The United States Patent Publication Nos. 20050123828 to Oogami et al. and 20050271934 to Kiger et al. present several disadvantages such as failure to provide a battery assembly with self-locating mechanical elements aimed to increase structural integrity of the battery assembly required while individual cells of the battery assembly are transported between various locations and do not reduce the weight of the battery assembly.
But even to the extend of being effective in certain respects, there is a constant need in the area of the battery art for an improved design of a battery pack having effective packaging characteristics, structural integrity thereby eliminating problems associated with current designs of prior art battery packs.